1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method of determining transmit power of an uplink control channel in a wireless communication system, and an apparatus using the method.
2. Related Art
3rd generation partnership project (3GPP) long term evolution-advanced (LTE-A) supports a carrier aggregation in which a plurality of carriers are aggregated and allocated to a user equipment.
A carrier used in the carrier aggregation may be a carrier which uses a time division duplex (TDD)-based frame (i.e., a TDD frame). The TDD frame may have various uplink (UL)-downlink (DL) configurations. In TDD, it is conventionally assumed that each carrier has the same UL-DL configuration in the carrier aggregation. However, it is recently considered to aggregate carriers having different UL-DL configurations.
Meanwhile, a wireless communication system may use a hybrid automatic repeat request (HARQ). The HARQ is a scheme in which a transmitter transmits data and thereafter receives acknowledgement/not-acknowledgement (ACK/NACK) as reception configuration information for the data, and transmits new data or retransmits previously transmitted data according to the ACK/NACK.
The ACK/NACK may be transmitted through an uplink control channel. In this case, transmit power of the uplink control channel may be determined on the basis of a parameter dependent on a physical uplink control channel (PUCCH). In TDD, the parameter may be defined differently according to the number of DL subframes (the number is denoted by M) matched to uplink subframes in which the ACK/NACK is transmitted.
When carriers having different UL-DL configurations are aggregated in TDD, the value M may vary in the same UL subframe of each carrier. Accordingly, this is necessarily considered in a method required for determining transmit power of a UL control channel.